1. Field of the Invention
This invention relates to silicone elastomer compositions having improved flame retardance.
2. Description of the Prior Art
The need for flame-retardant silicone elastomer compositions has been partially met by certain compositions of the art. Noble, et al., U.S. Pat. No. 3,514,424 teaches a composition of matter which in a cured state exhibits improved flame-retardant properties comprising an organopolysiloxane gum, a finely divided, non-alkaline inorganic filler and a small but effective amount to impart flame retardancy of a platinum-containing material. Up to 2/3 of the total silica filler can be replaced by such materials as carbon black, titanium dioxide or diatomaceous earth or a combination of these materials. Harder, U.S. Pat. No. 3,652,488 teaches a flameresistant composition consisting essentially of a polydiorganosiloxane gum, a reinforcing silica filler, an organic peroxide, an unsupported platinum-containing material and from 0.05 to 2 parts by weight of carbon black being essentially free of sulfur. Laur, et al., U.S. Pat. No. 3,635,874 shows a flame-resistant silicone composition consisting essentially of a polydiorganosiloxane gum, an organic peroxide, an unsupported platinum-containing material, from 0 to 100 parts of a reinforcing silica filler and from 0.5 to 100 parts of a fume titanium dioxide having an average particle diameter of less than 0.10 micron. Pfeifer, et al., U.S. Pat. No. 3,711,520 discloses a composition of matter which in the cured state exhibits improved flame-retardant properties comprising an organosiloxane gum, a finely divided, non-alkaline inorganic filler, a platinum-containing material and a small but effective amount to improve flame retardancy of the above composition of a Group II metal oxide not to exceed 100 parts by weight based on the organopolysiloxane gum. Up to 2/3 of the total silica filler can be replaced by such materials as carbon black, titanium dioxide or diatomaceous earth or a combination of these materials. Milbert, U.S. Pat. No. 3,821,140 provides an organopolysiloxane composition curable on heating to an elastomer comprising at least one diorganopolysiloxane rubber, at least one inorganic filler selected from the group consisting of pyrogenic silica, precipitated silica, reinforcing carbon black, diatomaceous silica, ground quartz, iron oxide, titanium dioxide, and calcium carbonate, an organic peroxide, a compound of platinum and either 3 to 35 parts in total of at least one rare earth metal oxide or 1 to 8 parts in total of at least one rare earth metal hydroxide.
Increasingly stringent safety concerns have made it desirable to have silicone compositions which provide better flame retardance than what is presently available from certain compositions of the art. For example, the peroxide of choice for curing silicone compositions is often, for various reasons, 2,5-bis (tertiary butyl peroxy)-2,5-dimethylhexane, which gives a cured silicone elastomer with relatively poor flame retardance. It would be desirable to provide a more flame-retardant silicone composition that has been cured with 2,5-bis(tertiary butyl peroxy)-2,5-dimethylhexane.